Wrong call to return
IT was a once-in-a-lifetime flood – twice in a month – that caught most off guard.
On Tuesday afternoon, residents in Lismore were told they could go home with caution as an earlier evacuation order was lifted, only for it to be reinstated at 3am on Wednesday. The Bureau of Meteorology got its forecast wrong.
Acting NSW Premier Paul Toole defended the failures, saying “no one could have predicted” the catastrophic weather, but one meteorologist could see what was coming: a hybrid cyclone.
“My jaw dropped last night when I saw the ‘all clear’ message given for residents to return to evacuated areas with the low hurtling towards the NE NSW coastline,” meteorologist Anthony Cornelius, from independent meteorological group Weatherwatch, posted. “As expected, the low has generated further torrential rain.
“I don’t want to throw people under buses, but what we saw, we had this obvious lowpressure system that became dominant east of Brisbane and was tracking southwest towards the northeast NSW coastline.”
But it was not behaving like a traditional east-coast low, which usually causes heavy rain and strong winds on its southern underside. “Going by
the satellite images … we saw most of the strongest heavy shower and storm activity sitting on the western edge of the low,” Mr Cornelius said.
“So the western side of the low was the concern and that was towards Lismore.”
Hence his surprise that the State Emergency Service gave the all clear for residents to return home Tuesday afternoon.
“All I can say, based on the information that we saw, there was a reasonable chance that the rain was going to be further
north to where they expected, which was that Wilsons River catchment,” Mr Cornelius said.
The catchment copped over 400mm and the Wilsons River again breached the levee and peaked at 11.40m around 5pm Wednesday, submerging the CBD and again flooding homes in low lying areas.
“There are two types of main systems we see along the east coast,” Mr Cornelius said.
“You have your east-coast lows that we are familiar with and you have your tropical cy
clones. Hybrid cyclones are a cross between the two systems. It doesn’t quite fit in the eastcoast low category but definitely doesn’t fit in the tropical cyclone category either.
“The hybrid systems play by different rules and this was a hybrid system because classic east-coast lows, the southern side of the system, is the danger zone. We had gale force westerly winds and torrential rains in Byron Bay which is unusual for an east-coast low.
“The system was not behav
ing as it should have during the Tuesday afternoon and, as a forecaster, you have some alarm bells in your head.”
A BOM spokeswoman said the term “hybrid cyclone” was not a defined term at the bureau, which has referred to the system that hit northern NSW as a “low-pressure system” and “continued to update its forecasts and warnings for the Northern Rivers as new information came to hand with what was a rapidly evolving and dynamic weather system”.